Molecular and cellular biology of the heat-shock response

Heat stress delays detoxification of phenanthrene in the springtail Folsomia candida

Climate change has intensified the occurrence of heat waves, resulting in organisms being exposed to thermal and chemical stress at the same time. The effects of mild heat shock combined with sublethal concentrations of phenanthrene (PHE) on defense mechanisms in springtails Folsomia candida were investigated. The transcription of Heat Shock Protein 70 (HSP70) was significantly upregulated by heat shock but tended to reach the control levels after 42 h of recovery. The transcription of cytochrome P450 3A13 (CYP3A13) was upregulated 3-13 fold by PHE but suppressed by heat shock. The suppression by heat shock might contribute to the reduced detoxification of PHE during high-temperature exposure. In line with this, we found that the internal PHE concentration was approximately 70% higher in heat-shocked springtails than in animals kept at control temperature. In general, the transcription of genes encoding enzymes of detoxification phase Ⅱ (glutathione S-transferase 3) and phase Ⅲ (ABC transporter 1) and the activity of antioxidant defense enzymes (superoxide dismutase and catalase) were less influenced than genes encoding phase I detoxification mechanisms (CYP3A13). These results indicate that heat shock delays the detoxification of PHE in springtails.

Are Hsp70 protein expression and genetic polymorphism implicated in multiple sclerosis inflammation?

Genetic and environmental factors contribute to disease Multiple Sclerosis (MS) susceptibility, the most prevalent neurological pathology affecting young individuals in Western countries. We focused our attention on HSP70-2, an inducible chaperon induced under stress conditions. Genotype analysis of HSP70-2 (+1267 A/G) polymorphism revealed a significant association between the minor allele G and presence of MS (OR:1.31, 95% CI: 1.02-1.69, P = 0.039). In addition, Hsp70-2 protein content in vitro from PBMC was significantly lower in MS patients with GG genotype compared to AA genotype, indicating an implication of the G allele of HSP70-2 gene polymorphism in the development of MS.

Genetic engineering for stress tolerance in the Triticeae

Genetic variation within a crop species is often limited and restricts improvement by conventional breeding methods. This is particularly true for environmental stresses, both biotic and abiotic. Wild relatives of crop plants, however, provide a rich source of novel variation which can be introduced into the crop. Many alien genes for biotic stress resistance have already been introduced into crops; in contrast, the genetic control of abiotic stress tolerance is poorly understood. Genetic engineering of abiotic stress tolerance in the Triticeae is the main subject discussed here with particular reference to salt tolerance in wheat and barley. Methods of alien gene transfer, including locating tolerance genes and restructuring chromosomes, are described. One of the major limitations in transferring genes for stress tolerance is the lack of good tests for resistance or tolerance which is largely due to the fact the physiological mechanisms involved are not fully understood. Genetic markers provide a new opportunity of detecting chromosome segments carrying desired genes easily and efficiently, and these will become increasingly important as the genetic maps of crop species are expanded. Although many stress genes have been located to specific chromosomes, and some have been mapped intra-chromosomally and their dominance relations determined, there is a great lack of knowledge of the control of these genes at the molecular level. Molecular studies of this type are difficult, but it is anticipated that the limitations will be overcome in the near future.

Association analysis of heat shock protein 70 gene polymorphisms in schizophrenia

OBJECTIVES

Heat shock proteins (HSPs) are a promising candidate gene in schizophrenia as they are believed to play a protective role in the central nervous system. An alteration in the titers of antibodies to the HSPs in schizophrenia patients has been suggested. Association between the three polymorphisms of HSP70-1 (HSPA1A), HSP70-hom (HSPA1L) and HSP70-2 (HSPA1B) and schizophrenia has been reported. Therefore, this study investigated the association between an enlarged set of SNPs at HSP70 gene and schizophrenia.

METHODS

Two hundred and ninety-four patients with schizophrenia and 287 controls were enrolled in the study. Genotypings of 5 SNPs of HSP70 were performed using pyrosequencing method. Haploview 3.2 was used to generate a linkage disequilibrium map and to test for Hardy-Weinberg equilibrium. Single locus and haplotype-based associations were tested. Tests for associations using and multi-marker haplotypes were performed by using a COCAPHASE v2.403. Association of SNP markers and clinical variables were analyzed by analysis of variance.

RESULTS

Significant association was detected at rs2075799 (allele A, X2 = 8.03, df = 1, P = 0.0046), but not at rs2227956 (P = 0.28), rs1043618 (P = 0.88), rs562047 (P = 0.47) or rs539689 (P = 0.32). In fact, the rs2075799*G/A genotype was more represented in patients with schizophrenia than in controls (X2 = 8.23, df= 1, P = 0.0041). Haplotype based associations were also detected (global P value 0.000003); the T-A-C-C-G haplotype was more prevalent among the patients (odds ratio, OR 5.95). Sliding windows analysis revealed a major contribution from rs2227956 and rs2075799 (global-P value 0.0075), with T-A haplotype significantly associated with schizophrenia. There was no evidence of an association between the clinical variables and schizophrenia across the genotypes.

CONCLUSION

Our results raise the possibility that HSP70 gene (i.e., haplotypes of rs2075799) might be implicated in the development of schizophrenia, although limited by rare haplotypic association with the disease. Hence further studies from different ethnics should be performed to confirm these results.

Mechanisms of temperature adaptation in poikilotherms

For good function, membrane lipids have to be arranged appropriately and be in the correct physical state. In poikilotherms, exposure to cold stress or heat shock can alter membrane properties such that, unless they are corrected quickly, damage and, possibly, death can result. Low temperature stress is countered by modifying membrane lipids such that their average transition temperature is lowered. There are various ways in which this can be achieved but an increase in fatty acid unsaturation is the most common. For heat shock, various changes in lipids have been noted and some defensive strategies involving heat shock proteins noted. In this short review, we will describe recent results where adaptive lipid changes, as a result of temperature stress, have been found. Mechanisms for bringing about such alterations are discussed, together with the contrasting data for different organisms.

The effect of early-age food restriction on heat shock protein 70 response in heat-stressed female broiler chickens

1. This study was conducted to determine the effect of early-age food restriction on heat shock protein (hsp) 70 synthesis in the brains of female broiler chickens exposed to high ambient temperatures. 2. Chicks were brooded for 3 weeks and then maintained at 24+/-1 degrees C. 3. On d 0, chicks were assigned to one of 4 feeding regimens; each regimen was applied to 4 cages of chicks. The regimens were: (1) ad libitum feeding (AL); (2) 80% food restriction at 4, 5 and 6 d of age (F80); (3) 60% food restriction at 4, 5, and 6 d of age (F60); and (4) 40% food restriction at 4, 5 and 6 d of age (F40). From d 35 to d 41, all chicks were subjected to 38+/-1 degrees C for 2 h/d. 4. One day following food restriction (d 7), hsp 70 expression in the brain samples of F60 and F40 chicks was augmented but not those fed AL and F80. 5. Prior to the heat challenge (d 35), all chicks had similar hsp 70 response. Irrespective of feeding regimen, there was a marked increase in hsp 70 expression after 4 d of heat treatment (d 38). Following 7 d of heat exposure (d 41), except for the F60 chicks, the augmented hsp 70 expression in the brains of AL, F80 and F40 birds was not maintained. 6. Enhancement of hsp 70 expression was noted in birds subjected to F60, but not AL, F80 or F40, throughout the period of heat exposure.

Identification of antibodies to heat shock proteins 90 kDa and 70 kDa in patients with schizophrenia

OBJECTIVES

Recent reports of antibodies to heat shock proteins 60kDa (HSP60) and HSP70 suggested that antibodies to the heat shock protein that plays a protective role against environmental stresses in a cell might be related to the pathogenesis of schizophrenia, although the antibody to HSP90 had not yet been identified in patients with schizophrenia. In this study, we tried to elucidate the specific involvement of the autoimmunity to HSPs in the pathogenesis and development of schizophrenia.

METHODS

Antibodies to HSP90 and HSP70 in 90 patients with schizophrenia and in 83 normal controls were measured by enzyme-linked immunosorbent assay (ELISA) coupled with the avidin-biotin system. In the patients, the association between antibody levels and clinical variables were sought. In addition, changes in antibody levels after treatment with antipsychotic medication were investigated.

RESULTS

Eighteen (20.0%) of the 90 patients showed 'high' levels of antibody to HSP90 above a cutoff value, and 28 (31.1%) of those showed 'high' antibody levels to HSP70. On the other hand, only four (4.8%) of the normal controls showed 'high' HSP90 antibody levels, and one (1.2%) of these showed 'high' antibody level to HSP70. The distribution of elevated HSP90 antibody was significantly associated with that of elevated HSP70 antibody in the patients with schizophrenia. The patients with 'high' levels of antibody to HSP70 showed higher initial Brief Psychiatric Rating Scale (BPRS) scores and showed greater clinical improvement than those with 'low' levels, while the patients with 'high' levels of antibody to HSP90 did not. The frequency of patients with high levels of antibody to HSP70 was decreased significantly after 6 weeks of antipsychotic treatment, while the frequency of patients with high levels of antibody to HSP90 was not.

CONCLUSIONS

Our results presented the presence of abnormal immune reactivity involving antibody to HSP90 and antibody to HSP70 in a subset of patients with schizophrenia. Differential patterns of distribution, of the association with clinical symptom severity, and of the changes of levels with treatment suggested the possibility that these two antibodies might be involved specifically in the pathogenesis of schizophrenia.

Heat shock protein 70 levels in rainbow trout primary epidermal cultures in response to 2,4-dichloroaniline exposure: a novel in vitro aquatic toxicity marker

The aim of this work was to investigate the use of the heat shock protein, HSP 70, as a sublethal measurement of ecotoxicity and to identify if the amount of HSP 70 synthesized is proportional to the chemical stress applied. This was achieved by quantifying the HSP 70 levels in primary cultured rainbow trout, Oncorhynchus mykiss (R.), skin epidermal cells in response to 2,4-dichloroaniline (2,4-DCA) exposure. The cellular stress response protects organisms from damage resulting from exposure to a wide variety of stressors including xenobiotics. The use of a HSP 70 polyclonal antibody on rainbow trout primary epidermal skin cultures exposed to 2,4-DCA was investigated as a possible biomarker for environmental stress using an immunocytochemical approach. The epidermis is highly susceptible, as it is the interface between the fish and its aquatic environment. In this study we have developed a simple in vitro system for aquatic-toxicity risk assessment. A method for the quantification of heat shock (stress) protein levels by immunocytochemistry is described. The antibody dilution range enabled the detection and quantification of only the inducible HSP 70 fraction. A 1:2000 dilution was decided upon. This assay was effective in detecting and quantifying the induced HSP 70. There was a direct toxicant concentration-dependent increase in the levels of the cellular stress protein in the primary epidermal cultures. Enhanced localization of HSP 70 in the nuclei of the epidermal cells was observed following exposure to 2,4-DCA. This work indicated the possibility of using heat shock protein induction and subsequent quantification as a sensitive system for aquatic toxicity risk assessment.

Response of high mobility group proteins of human kidney T1 and murine L 929 cell lines to heat shock

High mobility group (HMG) proteins in human kidney T1 and murine L 929 cells have been investigated after exposure to heat shock at 41 degrees C and their influence on the organizational change of chromatin under heat shock condition has been examined. Results reveal that the two cell lines show differential response of the HMG proteins 1 & 2 and 14 & 17 to heat shock. Neither T1 nor L 929 cells show significant differences in response to heat shock with respect to the binding affinities of HMG proteins 1 & 2 or 14 & 17 to DNA, as revealed by DNase I sensitivity and chromatin reconstitution assays. Furthermore, the HMG proteins of both the non-heat shocked and the heat shocked T1 and L 929 cells can recover their chromatin activity following reconstitution. These findings suggest that although the HMG proteins might undergo some change in response to heat shock, their inherent potential of reassociation with DNA is still retained.

The role of fertility restoration in the maintenance of the inversion In(2L)t polymorphism in drosophila melanogaster

In order to explain the worldwide latitudinal distribution and seasonal fluctuations in In(2L)t frequencies in Drosophila melanogaster, fitness differences among In(2L)t and Standard (ST ) homo- and heterokaryotypes under high-temperature conditions were determined. Viabilities were measured for high-temperature treatment started at different juvenile stages. The capacity to restore fertility after high-temperature treatment was measured for adults and juveniles. Furthermore, genetic adaptation for increased temperature resistance for these traits was determined for strains which were reared at 33 degrees C for 10 generations. Whereas larva-pupa survival rates were high, highest juvenile mortalities and strongest karyotypic effects were observed during the pupal stage when preceding larval stages were reared at 33 degrees C. ST karyotypes showed lowest viabilities. Although mating rate was hardly influenced, sterility was induced for females and males after high-temperature treatment of adults as well as juveniles. Subsequent transfer to 25 degrees C, however, resulted in restored fertility in some of the individuals, depending on the length of the recovery period. Fertility restoration was significantly higher for heterokaryotype males and females. Heterokaryotype superiority for restored fertility as well as for viability was positively correlated with severity of the treatment. Ten generations of selection at 33 degrees C resulted in significant improvement of juvenile survival and fertility restoration for all karyotypes. These fitness components were positively correlated (r=0.91; P < 0.001), which might suggest pleiotropic effects. It is concluded that the capacity to restore fertility after heat stress is an important fitness component, especially with respect to the In(2L)t polymorphism. The observed heterokaryotypic superiority fits with the idea that the latitudinal distribution of In(2L)t frequencies is maintained by balancing selection, with equilibrium values decreasing with latitude.

Increased thermosensitivity associated with topoisomerase I deletion and promoter mutations in Escherichia coli

An Escherichia coli mutant with three of the promoters for the topoisomerase I gene (topA) deleted, such that only the sigma 32-dependent promoter (P1) remained, had a decreased level of topoisomerase I at 30 degrees C and showed increased thermosensitivity at 52 degrees C. However, it could still develop thermotolerance and had a wild-type level of resistance to 52 degrees C treatment if exposed first to 42 degrees C. This indicated that newly synthesized topoisomerase I from transcription initiated at P1 was important for development of thermotolerance. Two other E. coli mutants lacking topA were > 100 times more sensitive to high temperature than their wild-type isogenic strains.

Ability of laying hens to jump between perches: individual variation and the effects of perch separation and motivation on behaviour

1. This study investigated the ability and the behaviour of laying hens jumping between perches 2 different distances apart using hungry and satiated birds to determine whether behaviour and success were related to motivation. 2. Four groups of 10 birds (Lohmann brown) trained to jump from one perch to another were subjected 4 times to each of the experimental treatments (2 perches with a distance of either 50 or 150 cm between them) whilst either hungry or satiated, controlling for time of day and order of presentation. 3. The behaviour of each bird on the 1st perch was observed for a maximum of 2 min or until the bird jumped from the perch. The outcome of each jump, number of head movements and steps, incidence and duration of calling, and activity score were recorded. 4. The probability of birds jumping was less at the greater distance and was not affected significantly by other experimental factors. 5. Head movements were more frequent in birds which jumped, at the shorter distance, in motivated (hungry) birds and in the morning rather than the afternoon. 6. More stepping was performed by birds which jumped and at the shorter distance; there was no significant effect of motivation or time of day on stepping rate. 7. Birds called more at the greater distance and this was interpreted as indicative of frustration. 8. Subjective scores for activity were lower when perches were separated by the greater distance and when birds were satiated (less motivated) rather than hungry. 9. Agitated head movements and stepping activity thus occurred mainly when birds were motivated and on the point of jumping whereas calling was associated with an apparent inability or unwillingness to jump.

Hepatic concentration of heat shock protein 70 kD (Hsp70) in broilers subjected to different thermal treatments

1. The relationship between repeated thermal treatments and hepatic synthesis of Hsp 70 was studied in broiler chickens. 2. Sixty broilers were submitted to 5 different treatments (12 birds each) from day 1 to day 42. Four groups were kept in a thermoneutral environment and subjected to 0, 1, 2 and 3 heat stress episodes at 35 degrees C for 4 h per week (TN-0, TN-1, TN-2 and TN-3, respectively). The last group (HT-35) was reared at a room temperature of 35 degrees C. 3. From 39 to 42 old, the birds experienced acute heat stress at 41 degrees C. Resistance to heat stress was evaluated by the time taken for rectal temperature to increase by 3 degrees C above the pre-treatment value. Livers were collected (before and after heat stress) and Hsp70 was determined using Western Blot analysis with monoclonal anti-Hsp70 antibody. 4. Resistance to heat stress and concentration of Hsp70 were higher in those birds subjected to more heat stress episodes during the experimental period (TN-3) and HT-35. A positive correlation was observed between Hsp70 concentration and the time taken for a 3 degrees C increase in rectal temperature (r = 0.42; P<0.01). 5. Exposing birds to episodes of heat stress (35 degrees C) during rearing may improve their resistance to acute heat stress, but the previous thermal history did not seem to influence the hepatocyte Hsp70 content after exposure to more severe heat stress (41 degrees C).

Heat-shock proteins, molecular chaperones, and the stress response: evolutionary and ecological physiology

Molecular chaperones, including the heat-shock proteins (Hsps), are a ubiquitous feature of cells in which these proteins cope with stress-induced denaturation of other proteins. Hsps have received the most attention in model organisms undergoing experimental stress in the laboratory, and the function of Hsps at the molecular and cellular level is becoming well understood in this context. A complementary focus is now emerging on the Hsps of both model and nonmodel organisms undergoing stress in nature, on the roles of Hsps in the stress physiology of whole multicellular eukaryotes and the tissues and organs they comprise, and on the ecological and evolutionary correlates of variation in Hsps and the genes that encode them. This focus discloses that (a) expression of Hsps can occur in nature, (b) all species have hsp genes but they vary in the patterns of their expression, (c) Hsp expression can be correlated with resistance to stress, and (d) species' thresholds for Hsp expression are correlated with levels of stress that they naturally undergo. These conclusions are now well established and may require little additional confirmation; many significant questions remain unanswered concerning both the mechanisms of Hsp-mediated stress tolerance at the organismal level and the evolutionary mechanisms that have diversified the hsp genes.

Nongenetic variation, genetic-environmental interactions and altered gene expression. II. Disease, parasite and pollution effects

The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, there are many confounding factors that may alter the results of an electrophoretic study and may possibly allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Measured enzyme activities can also be affected significantly. Parasites, disease and pollution can affect levels of enzyme activity, and electrophoretic results can be affected both quantitatively and qualitatively. Blood serum is particularly vulnerable to variation to variation due to disease, pollution or parasites because damaged tissues may release tissue-specific enzymes into the bloodstream. Capture, handling, chemical treatments, bacteria, natural toxins and consumed food may also contribute to variation. Potential pollution impacts at specimen collection sites should be investigated, and study organisms should be inspected and/or treated for detection and elimination of parasites and disease.

Heat stress lipids and schizophrenia

The neurodevelopmental hypothesis of schizophrenia implicates abnormal or disrupted neural growth during embryogenesis. It is postulated here that stress-inducing agents acting upon a compromised cellular system resulting from abnormal plasma membrane lipids could effect the neuronal abnormalities observed in schizophrenia. The heat stress response is induced by exposure to hyperthermia as well as a variety of other agents. The response to these agents includes the cessation of most transcriptional and translational activities, accompanied by the induction of a highly specific set of proteins. A concomitant reduction in metabolic activity including cell cycle delays is also observed. Much of the enormous literature on the heat stress response concentrates on protein and DNA interactions, especially with regard to transcriptional control. However, a variety of lipids are intrinsically involved in the heat stress response. This paper will provide a brief introduction to the heat shock proteins and will explore the roles that lipids play in the heat shock response.

Environmental health science research and human risk assessment

Environmental health science research, with its focus on fundamental science and disease prevention, is important for the development of rational and cost-effective public health and regulatory policies related to environmental protection. Environmentally related diseases are preventable, yet they impose a major burden on society in terms of human suffering and costs related to health care. Similarly, the expenditure of hundreds of billions of dollars for regulatory compliance is a major economic concern. There is considerable debate regarding current regulatory risk assessment practices for environmental agents. Implicit in all risk assessment schemes is the need to extrapolate from high-exposure studies to low-exposure situations and from known risks in rodents to probable risks in people. Both extrapolations are fraught with uncertainties. These uncertainties are accommodated in risk-assessment schemes by the incorporation of arbitrary "safety factors" and other default approaches. Since these factors are not derived experimentally, they may overestimate or under estimate actual risks. Risk-assessment methodology, its relevance to the human condition, and its use in protecting human health will greatly improve when our expanding knowledge of the basic biology of environmental effects is incorporated into toxicological testing and risk-assessment schemes. Moreover, exciting opportunities now exist to advance our understanding of the environmental and genetic bases of many common diseases and to design effective prevention and intervention strategies to combat their development. This report discusses some of the current opportunities and challenges.

Differential effects of hyperthermia on macrophage interleukin-6 and tumor necrosis factor-alpha expression

The pyrogenic cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) appear in the circulation during infections and injuries, but TNF-alpha and IL-6 are regulated differently in macrophages. We compared the effects of elevated temperatures within the usual febrile range on the expression of TNF-alpha and IL-6 in vitro in lipopolysaccharide (LPS)-stimulated human macrophages derived from peripheral blood monocytes (HuMoM phi). During an 18-h incubation at 37 degrees C with 5 ng/ml LPS, these cells released 5,030 +/- 1,460 pg TNF-alpha/10(6) cells (means +/- SE) and 1,380 +/- 280 pg IL-6/10(6) cells. In LPS-stimulated HuMoM phi incubated at 40 degrees C, TNF-alpha release was almost completely inhibited (76 +/- 76 pg TNF-alpha/10(6) cells; P < 0.01 compared with LPS-stimulated HuMoM phi at 37 degrees C), but release of IL-6 was preserved (1,600 +/- 780 pg IL-6/10(6) cells). Western and Northern analyses showed that levels of TNF-alpha mRNA and cell-associated and secreted TNF-alpha protein were decreased, but IL-6 expression was unchanged at 40 degrees C in LPS-stimulated macrophages. Incubating HuMoM phi at 40 degrees did not alter their viability after 18 h but induced a 75-fold increase in levels of the inducible heat-shock protein 72 (HSP-72) mRNA in the face of a 56% inhibition in total protein synthesis. Our results show that IL-6 expression persisted at incubation temperatures in the upper end of the physiological range that induced heat shock and attenuated the expression of functionally active TNF-alpha in LPS-stimulated HuMoM phi.

Gene expression under temperature stress

In this review, changes in plant gene expression in response to environmental stresses are discussed using the examples of high and low temperature treatments. While some changes may contribute to acclimatory processes which improve plant survival or performance under stress, others may be 'shock' responses indicative of sensitivity. The heat-shock response, which is almost ubiquitous among eukaryotic organisms, is characterized by repression of normal cellular protein synthesis mediated at both the transcriptional and the translational level, and induction of heat-shock protein (HSP) synthesis. There is a correlation between HSP synthesis and induced thermotolerance in plants, but the evidence for a causal relationship is not conclusive. The possible biochemical functions of some of the HSPs are now becoming apparent; they are believed to play an important role in preventing accumulation of damaged proteins in the cell during heat shock. Although no other environmental stress elicits the full heat-shock response, certain treatments do induce synthesis of subsets of the HSPs, and the reasons for this are considered. Alterations in gene expression in response to low temperatures are more diverse and usually less dramatic than the heat-shock response, with which they share little, if any, homology. Biochemical adjustments during cold treatment are discussed, with particular reference to those which contribute to acclimation. Several genes whose expression is induced by cold have been cloned and characterized, and in some cases it is possible to attribute in vivo functions to them; they include enzymes of lipid, carbohydrate and protein metabolism, structural proteins and putative cryoprotectants. The use of transgenic plants is further facilitating an investigation of the biochemical factors which are important in cold acclimation. Drought, osmotic stress and abscisic acid induce expression of many of the same genes as does cold treatment; it seems likely that some of the products of these genes contribute to increased freezing tolerance by protecting against intracellular dehydration. Contents Summary 1 I. Introduction 1 II. High temperature stress 3 III. Low temperature stress 10 IV. Concluding remarks 20 Acknowledgements 21 References 21.

Quantitative expression of maize HSPs: genetic dissection and association with thermotolerance

In higher plants, within-species qualitative polymorphism for heat shock proteins (HSPs) is extremely rare, even between genotypes showing different heritable levels of thermotolerance. Here we have explored the amount of quantitative variability in HSP synthesis in maize. We have analyzed the quantitative expression of the typical HSPs in a set of recombinant inbreds (RIs) derived from the f1 hybrid between a thermotolerant (T232)- and a thermosensitive (CM37)-genotype, characterized for about 200 mapped RFLP loci. Significant differences were detected in the level of expression of five HSPs, and their frequency distribution in the RI population is that of a quantitative trait. Subsequent mapping of loci controlling the characters, based on RFLP analysis, confirmed the multigenic control of HSP expression: the regression analysis of the band intensities of each variant HSP on RFLPs revealed, for the different HSPs, a minimum number of three to eight quantitative trait loci (QTLs) accounting for a high proportion (0.35-0.60) of the genetic variability of these bands. An analysis of the correlation between the variability of HSPs and that of cellular membrane stability, a cellular component of thermotolerance, did not reveal any significant association of the two parameters.

A pathogen-induced gene of barley encodes a HSP90 homologue showing striking similarity to vertebrate forms resident in the endoplasmic reticulum

The full-length nucleotide sequence of a barley (Hordeum vulgare L.) leaf mRNA, found to increase rapidly in amount during infection attempts by the powdery mildew fungus (Erysiphe graminis DC. ex Mérat), is reported. The mRNA encodes a polypeptide of 809 amino acid residues which, by sequence comparison, was identified as a member of the 90 kDa heat shock protein (HSP90) family. The encoded protein most resembles the endoplasmic reticulum (ER) resident HSP90 protein, the 94 kDa glucose-regulated protein (GRP94) of vertebrates, as it possesses both the characteristic N-terminal domain including a signal peptide sequence and the C-terminal ER retention signal (Lys-Asp-Glu-Leu). A transcript cross-hybridizing at high stringency accumulated rapidly in leaves upon heat shock treatment. Genomic DNA blot analysis indicated the presence of a family of related genes in the barley genome.

Heat shock proteins in three related Drosophila species belonging to the obscura group

The effect of heat shock on protein synthesis in three related Drosophila species belonging to the obscura group was analyzed on SDS-acrylamide gels. Four major heat shock proteins (hsps) were found in these species, in which synthesis reaches a maximum at 34 degrees C. Although the higher molecular weight proteins are conserved, differences in size were found for the small hsps in these species. By means of in situ hybridization using D. melanogaster probes for the small hsp genes, it was inferred that the small hsp genes of the obscura group species are clustered at the 27A locus in all three species.

Characterization of the heat shock response in Enterococcus faecalis

We have characterized the general properties of the heat shock response of the Gram-positive hardy bacterium Enterococcus faecalis. The heat resistance (60 degrees C or 62.5 degrees C, 30 min) of log phase cells of E. faecalis grown at 37 degrees C was enhanced by exposing cells to a prior heat shock at 45 degrees C or 50 degrees C for 30 min. These conditioning temperatures also induced ethanol (22%, v/v) tolerance. The onset of thermotolerance was accompanied by the synthesis of a number of heat shock proteins. The most prominent bands had molecular weights in the range of 48 to 94kDa. By Western blot analysis two of them were found to be immunologically related to the well known DnaK (72kDa) and GroEL (63kDa) heat shock proteins of Escherichia coli. Four other proteins showing little or no variations after exposure to heat are related to DnaJ, GrpE and Lon (La) E. coli proteins and to the Bacillus subtilis sigma 43 factor. Ethanol (2% or 4%, v/v) treatments elicited a similar response although there was a weaker induction of heat shock proteins than with heat shock.

Differences in the heat-shock response between thermotolerant and thermosusceptible cultivars of hexaploid wheat

Heat-shock protein (HSP) gene expression in two wheat lines cv 'Mustang' (heat-tolerant) and cv 'Sturdy' (heat-susceptible) were analyzed to determine if wheat genotypes differing in heat tolerance also differ in in-vitro HSP synthesis (translatable HSP mRNAs) and steady-state levels of HSP mRNA. Several sets of mRNA were isolated from seedling leaf tissues which had been heat-stressed at 37 °C for various time intervals. These mRNAs were hybridized with HSP cDNA or genomic DNA probes (HSP17, 26, 70, 98, and ubiquitin). Protein profiles were compared using in-vitro translation and 2-D gels. The Northern slot-blot data from the heat-stress treatment provide evidence that the heat-tolerant cv 'Mustang' synthesized low molecular weight (LMW) HSP mRNA earlier during exposure to heat shock and at a higher level than did the heat-susceptible cv 'Sturdy'. This was especially true for the chloroplast-localized HSP. The protein profiles shown by 2-D gel analysis revealed that there were not only quantitative differences of individual HSPs between the two wheat lines, but also some unique HSPs which were only found in the 'Mustang' HSP profiles. The high level of RFLP between the two wheat lines was revealed by Southern blot hybridization utilizing a HSP17 probe. These data provide a molecular basis for further genetic analysis of the role of HSP genes in thermal tolerance in wheat.